Art of producing polymers of acrylonitrile



United States Patent 3,028,372 ART OF PRODUCING POLYMERS 0F ACRYLONITRILE Witoid R. Kocay, Stamford, Conn, and Marvin Wishman, White Plains, N.Y., assignors to American Cyanamid Company, New York, N.Y., a corporation of Maine N0 Drawing. Continuation of application Ser. No. 711,117, Jan. 27, 1958. This application May 26, 1961, Ser. No. 112,750

7 Claims. (Cl. 260-805) This invention relates to the preparation of polymers. More particularly, the invention is concerned with certain new and useful improvements in a method of preparing a polymer of polymerizable material comprising at least one compound containing a CH =C grouping by polymerizing said polymerizable material in an aqueous medium at a pH not higher than about 4.0, using a particular polymerization catalyst system, namely, a redox-catalyst system comprising chlorate ions and sulfite ions. The invention is especially useful and valuable in the preparation of polymers (homopolymers and copolymers) of acrylonitrile.

Polymers of acrylonitrile and of other polymerizable organizable organic compounds containing at least one ethylenic bond are, of course, known. These polymers have achieved wide use in the production of many valuable commercial products, e.g., plastic and coating compositions, synthetic rubber, and, more recently, synthetic fibers.

Difiicuities have been encountered in polymerizing certain of the aforementioned polymerizable organic compounds, e.g., acrylonitrile alone and with other monomers, and especially in controlling the average molecular weight and molecular-weight distribution of the polymer; and considerable efiort has been spent in developing practical processes for preparing these extremely useful homopolymers and copolymers that would overcome these difficulties. Thus, recent developments in the polymerization of acrylonitrile have been concerned largely with poly:

merization in aqueous media, for instance, as described in Jacobson United States Patent No. 2,436,926, March 2, 19 48, Brubaker and Jacobson United States Patent No. 2,462,354, February 22, 1949, Rothreck United States Patent No. 2,640,049, May 26, 1953, and Scheiderbauer et al. United States Patent No. 2,748,106, May 29, 1956; and with the use of redox-catalyst systems that aim to give a high yield of polymer in a short time at a moderate temperature. Redox-catalyst systems comprising a peroxy compound and a sulfoxy compound, such as, for example, ammonium persulfate and sodium bi-sulfite, have been used for the homopolymerization and copolymerization of acrylonitrile and other vinyl compounds (see, for example, the aforementioned United States patents); and also redox systems comprising a water-soluble chlorate, e.g., sodium or potassium chlorate, and a water-soluble sulfite or bisulfite, e.g., sodium sulfite or bisulfite (see, for instance, Hill United States Patent No. 2,673,192, March 23, 1954, Cresswell United States Patent No. 2,751,374, June 19, 1956, and Maliison United States Patent No. 2,777,832, January 15, 1957).

The problems encountered in forming spinnable or fiber-forming (fiber-formable) polymers, more particularly copolymers of acrylon-itrile and a vinylpyridine, that are uniform from the standpoint of molecular-weightdistribution and structure, and in other characteristics, are

pointed out in the above-named Rothrock Patent No. 2,640,049.

The present invention is based on our discovery that, in a polymerization method of the. kind broadly described in the first paragraph of this specification, the

conversion of the polymerizable material (more particu- 3,028,372 Patented Apr. 3, 1962 larly a monomeric material) comprising at least one compound containing a CH =C grouping e.g., acrylonitrile, to polymer of substantially uniform average molecular weight can be increased by increasing the ratio of molar equivalents of sulfite ions to said polymerizable material together with an increase in the ratio of molar equivalents of chlorate ions to said polymerizable material that is greater than the increase in the ratio of molar equivalents of sulfite ions to said polymerizable material. This discovery was quite surprising and unexpected; in no way could have been predicted from the teachings of the prior art; and its practical advantages will be immediately apparent to those skilled in the art.

Contrary to the above findings, Scheiderbauer et al., supra, in acknowledging the prior art, stated that the only known method of increasing conversion was to increase the concentration of the redox catalyst system, which always resulted in increased yield of polymer, but the molecular weight of the polymer formed was inversely proportional to the yield. By the process of the invention of Scheiderbauer et al., using a difierent catalyst system, conversions were increased to about or more through increasing the concentration of the monomer in the reactant feed streams and suitably lowering the catalyst and activator concentrations relative to the monomer. (Parenthetically, it may be mentioned that another method for controlling molecular weight, apparently unknown to Scheiderbauer et al., has been to vary the acid-.

to-monomer ratio during polymerization.)

In marked contrast to the teachings of Scheiderbauer et al., by the use of the concept of the present invention the amount of total catalyst used in polymerization can be increased, without any substantial change in molecular weight, in the following Way:

If only the ratio of molar equivalents of chlorate ions to polymerizable material (i.e., ratio of chlorate to monomer) is increased, the molecular weight increases; and if only the ratio of sulfite ions to polymerizable material (i.e., ratio of sulfite to monomer) is increased, the molecular weight is decreased. Therefore, a proper simultaneous increase of both chlorate and sulfite will keep the molecular weight at the same level, but the total amount of catalyst added will be increased. Hence, contrary to the teachings .in the Scheiderbauer et a1. patent, supra, the percentage conversion of monomer to polymer can be increased by using more total catalyst (chlorate plus sulfite) without the deficiency noted by Scheiderbauer et alywith a different catalyst system. Furthermore, it has been found that if the chlorate and sulfite concentrations are increased to a sutficiently high degree, while continuing to maintain the desired molecular weight, the molecular weight then becomes completely independent of catalyst concentration, so that it is no longer effected by minor variations in the catalyst-feed rate. Thus, in practicing our invention and when holding all other conditions constant, there is an optimum chlorate-sulfite concentration (ratio of total chlorate plus sulfite to polymerizable material) above which concentration the molecular weight is no longer dependent on the catalyst (chlorate-sulfite) concentration so long as the molar ratio of chlorate to sulfite is not altered. This is shown more clearly in a table given as a part of Example 3. ,As shown by the aforementioned Hill, Cresswell, and Mallison patents, acidic aqueous catalyst systems containing reducible chlorate ions and oxidizable sulfoxy ions have been suggested for use in the polymerization of various vinyl compounds, including vinyl chloride, acrylonitrile, vinyl acetate, and others. The oxidizable sulfoXy ions used in such systems have generally been of the group consisting of sulfite, bisulfite, and hydrosulfite ions, and these same sulfoxy ions comprise a preferred group employed in practicing the present invention, but it is not intended that the invention shall be limited to the use of only this group. While the components of an oxidation-reduction or redox-catalyst system of this nature may be introduced as chloric and sulfurous acids, these acids are relatively unstable; therefore, it is usually more convenient to add the desired ions to the polymerization system in the form of a Water-soluble chlorate and a water-soluble salt containing the oxidizable sulfoxy ion, elg., a water-soluble sulfite, together with a suitable acid such, for instance, as sulfuric acid, phosphoric acid, bydrochloric acid, etc. During polymerization in an aqueous system containing a chlorate-sulfoxy catalyst combination, the chlorine is reduced and the sulfur simultaneously oxidized.

The improvement of the present invention is applicable in a polymerization method of the kind broadly described the first paragraph of this specification, and which can be carried out batchwise, semi-continuously or continuously. A continuous method is preferred. Polymerization can be effected while the polymerizable material (e.g., a single or a plurality of monomers) is dissolved or dispersed (as by emulsification, for example) in an aqueous medium having a pH of 4.0 or less, advantageously from about 2.0 to about 3.6. The reaction mass comprises the polymerizable material, the aforesaid aqueous medium and a redox-polymerization-catalyst system that includes, as essential components, (a) a Water-soluble chlorine compound that yields chlorate ions in an aqueous acidic medium and (b) a water-soluble sulfoxy compound that yields oxidizabie sulfoxy ions in an aqueous acidic medium. This aqueous acidic medium advantageously comprises an aqueous solution of a non-oxidizable acid having a dissociation constant greater than lO- e.g., sulfuric, nitric, phosphoric, hydrochloric, or other strong acid.

When the polymerization reaction is carried out continuously, one can, if desired or required, charge additional water to the reactor, separately or with one or another of the various feeds of the aforementioned ingredients, so that a desired concentration of materials in the aqueous medium is maintained in the reactor. It is usually preferable to limit the amount of Water so that the total weight of polymerizable monomers is between about 15% and 50% of the total material charged during the polymerization reaction. This is especially true when the polymerizable material comprises a substantial amount of acrylonitrile, since the resulting suspension of polymer then has excellent pumping characteristics, as well as outstanding drainage or filtering qualities. Additional economies are, of course, realized in that a small volume of the reaction mass is processed and handled. No difficulties are encountered With respect to separation of polymerizable material, since the polymerizable ingredient or ingredients are charged at arate which is correlated with the rate of polymerization in such a manner that separation of polymerizable material, specifically monomeric material, does not occur.

In the redox-polymerization-catalyst system employed, the amount of chlorate ions introduced to the reaction mass (reactor) generally will be between about 0.1% and about 2.0% of the Weight of the polymerizable monomeric material, and the oxidizable ions, specifically sulfoxy ions, will be present in a quantity ranging between about 0.1% and about 6% by Weight on the same basis. Larger amounts of the catalyst components, e.g., 3 or more percent of chlorate ions and 9 or more percent of sulfoxy ions, are operative, but appear to provide no additional benefits. When the oxidizing and reducing components are present in oxidation and reduction equivalents, then in the case of the preferred oxidizable component, 3 moles of the sulfurous acid or a sulfite react per mole of chloric acid or a chlorate. The ratio is the same for bisuliites, but only 1.5 moles of a metabisulfite are required, since such salts ionize to form HSO ions.

in the redox polymerization catalyst system used in practicing the present invention, any Water-soluble chlorine compound that yields chlorate ions in an aqueous acidic medium can be used, for instance: chloric acid, ammonium, and the various alkali-metal (sodium, potassium, lithium, etc.) chlorates; and the various watersoluble, alkaline-earth metal and heavy metal chlorates.

Illustrative examples of reducing agents that can be employed are sulfites, bisulfites, and metabisulfites corresponding to the chlorates named in the preceding paragraph, sulfur dioxide, and diethyl and other water-soluble dialkyl sulfites.

By the term sulfite ions as used herein and in the appended claims is intended to be included the various suifoxy species, more particularly H 50 and/or H50; and 50 the proportionate amounts of these species being a function of pH. We believe that the active component is probably the H 50 molecule.

Relatively loW polymerization temperatures, for example, temperatures ranging from about 20 C. to about 70 C, are desirable. larticularly good results are generally obtained when the temperature of polymerization is maintain-ed Within the range of from about 35 C. to about 65 C.

t is desirable to conduct the process of the present invention in the absence of oxygen, which has a definite inhibitin effiect on the polymerization reaction. Suitable inert gases, such as nitrogen and carbon dioxide, may be used to displace air in the reaction zone.

Polymerizable materials that can be polymerized (homopolymen'zed or copolymerized) include those mentioned in the aforesaid Hill, Cresswell, and Mallison patents. Other examples (some of which are named by Hill, Cresswell, or Mallison in the patents) are the vinyl aromatic and isopropenyl aromatic compounds, more particularly the different vinyl aromatic and isopropenyl aromatic hydrocarbons (e.g., the various dialkyl styrenes, isopropenyl toluene, etc.), other aliphatic compounds containing a CH =C grouping, e.g., the various substituted acrylonitriles (e.g., methacrylonitrile, ethaorylonitrile, phenylacrylonitrile, etc.), the various substituted acrylamides (e.g., methacrylamide, ethacrylamide, the various N-substituted acrylamides and N-substituted alkacrylamides, for instance, N-methylol acrylamide, N- monoalkyl and -dialky1 acrylamides and methacrylamides, e.g., N-rn'onomethyl, ethyl, -propyl, -butyl, etc., and N- dimethyl, -ethyl, -propyl, -butyl, etc., acrylamides and methacrylamides, N-monoaryl and -diaryl acrylamides and alkacrylamides, e.g., N-monophenyl and -diphenyl acrylamides and methacrylarnides, etc.), vinyl esters, e.g., vinyl acetate, vinyl chloroacetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl valerate, vinyl acrylate, vinyl methacrylate, etc., esters of an acrylic acid (including acrylic acid itself and the various alpha-substituted acrylic acids, e.g., methacrylic acid, ethacrylic acid, phenylacrylic acid, etc.), more particularly the alkyl esters of an acrylic acid, e.g., the ethyl, propyl, isopropyl, nbutyl, isobutyl, sec.-butyl, tert.-butyl, amyl, hexyl, heptyl, octyl, decyl, dodecyl, etc., esters of acrylic, methacrylic, ethacrylic, phenylacrylic, etc., acids including the alkyl acrylates containing not more than four carbon atoms in the alkyl grouping, examples of which are given above, diallyl amine, dimethallyl amine, vinyl ethyl ether, diallyl benzene, as Well as other vinyl aromatic and vinyl aliphatic compounds, and other compounds containing a CH =C grouping, more particularly a single CH =C grouping. Two, three, four, five, or any desired higher number of monomers can be admixed and copolymerized in accordance with the present invention. In producing fiberforming copolymers, and which preferably have an average molecular weight within the range of from, about 60,000 to about 90,000, We prefer that the modifying comonomer employed be one that contains a single CH =C grouping. The average molecular weight, as defined herein, is determined from an absolute viscosity,

. value of a 1% solution of the polymer in 50% aqueous sodium thiocyanate.

In practicing the present invention to produce fiberforming (fiber-formable) acrylonitrile copolymers, the monomeric material generally comprises more than 50%, more particularly at least 70% by weight of acrylonitrile, e.g., 100% acrylonitrile; or more than 50% by weight of acrylonitrile while the remainder is constituted of at least one other different compound which is copolymerizable with acrylonitrile and which contains a CH =C grouping. Thus, in addition to acrylonitrile, the polymerizablc material may include a plurality of difierent compounds which are copolyrnerizable with acrylonitriie and each one of which contains a 'CH =CH grouping, at least one of said compounds being a vinylpyridine. The present invention provides good results in preparing a copolymer of monomeric material comprising at least 80% by weight of acrylonitrile, from 2 to 15% by weight of a vinylpyridine, and from 2 to 15 by weight of vinyl acetate, methyl acrylate, acrylamide, methacrylamide, acrylic acid, methacrylic acid, methacrylonitrile, or the like.

Illustrative examples of vinylpyridines that can be copolymerized with acrylonitrile, alone or with one or more other copolymerizable monomers, by the method of the present invention, include vinylpyridines represented by the formula CH=CH and which include Z-Vinylpyridine, S-Vinylpyridine, and 4-vinylpyridine; methyl vinylpyridines represented by the formula II CII=CHZ C Ha and which include 2-methyl-3-vinylpyridine, 2-methyl-5- vinylpyridine, 3-vinyl-4-methylpyridine, 3-vinyl-5-methylpyridine, 2-vinyl-3-methylpyridine, 2-vinyi-4-methylpyridine, 2-vinyl-S-methyipyridine, 2-vinyl-6-methylpyridine, 2-methyl-4-vinylpyridine, and 3-methy1-4-vinylpyridine. The vinylpyridines embraced by Formula II are a preferred sub-group within a broader class of vinylpyridines that are advantageously employed in continuously making dyeable, fiber-forming binary and ternary polymers in accordance with the instant invention and which may be represented by the formula III CH=G1-12 wherein R represents a lower alkyl radical, more particularly a methyl, ethyl, propyl (including n-propyl and isopropyl) or butyl (including n-butyl, isobutyl, sec.-butyl and tert.-butyl) radical. Other examples include the 2- and 4-vinylquinolines, the various vinyl isoquinolines, 2- vinyl 4,6 dimethylpyridine, 2-vinyl-4,6-diethylpyridine, and others embraced by the formula IV CH=OH2 where R represents a lower alkyl radical, examples of which have been given hereinbefore, and n represents integer from 1 to 5, inclusive.

In order that those skilled in the art may better understand how the present invention can be carried into efiect, the following examples are given by way of illustration and not by way of limitation. All parts and percentages are by weight unless otherwise stated.

Example 1 (A) One hundred and fifty-two (152) parts (2.87 moles) of aorylonitrile, 8 parts (0.093 mole) of methyl acrylate, 1.2 parts (0.033 mole) of hydrogen chloride, and 1439 parts of deionized water are charged into a round-bottomed flask. The flask is placed in a constanttemperature bath, and a condenser, thermometer, stirrer, nitrogen-inlet tube, and dropping funnel are attached. The monomer mixture is heated at 40 C. under nitrogen for one hour. The catalyst, 0.546 part (0.00513 mole) of sodium chlorate and 4.52 parts (0.0359 mole) of sodium sulfite, is dissolved in cc. of Water into .the dropping funnel. Forty (40) percent of the catalyst, 60 cc. of solution, is rapidly added to the reaction vessel. After 25 minutes, an additional 22.5 cc. of catalyst solution is added. The remaining catalyst solution is added at 25-minute intervals in volumes of 22.5, 15, 15, 7.5, and 7.5 cc. Catalyst addition is complete in 2.5 hours. The mixture is agitated 1.5 hours longer, and the polymer is collected by filtration. The pH of the efiiuent mother liquor is 2.8. In this example, the mole ratio of sodium chlorate to monomer is 0.00173, while the mole ratio of sodium sulfite to monomer is 0.0121. Conversion of monomer to polymer is 79 percent of theory. The polymer has an average molecular weight of 80,500.

(E) The above example is repeated, except that 0.852 part (0.008 mole) of sodium chlorate and 5.04 parts (0.04 mole) of sodium sulfite are used. In this case, the mole ratio of sodium chlorate to monomer is 0.00270, while the mole ratio of sodium sulfite to monomer is 0.0135. Conversion of monomer to polymer is 86 percent of theory. The polymer has an average molecular weight of 80,500.

A comparison of the (A) and (B) portions of this example shows that the conversion of monomer to polymer is increased and the average molecular weight is maintained, despite the increase in total catalyst used, by increasing the mole ratio of sodium chlorate to monomer by 1.56-fold along with a simultaneous 1.2-fold increase of the mole ratio of sodium sulfite to monomer.

if the mole ratio of sodium chlorate and sodium sulfite to monomer are each increased in the same ratio, the average molecular weight decreases as expected.

(C) The (A) portion of this example is repeated, except that 0.716 part (0.00671 mole) of sodium chlorate and 5.93 parts (0.0470 mole) of sodium sulfite are used. In this case, the mole ratio of sodium chlorate to monomer is 0.00226, while the mole ratio of sodium sulfite to monomer is 0.0158. Conversion of monomer to polymer is 82 percent of theory. The polymer has an average molecular weight of 65,000.

A comparison of the (A) and (C) portions of this example shows that the average molecular weight or" polymer is decreased from 80,500 to 65,000 by increasing the mole ratios of sodium chlorate and sodium sulfite to monomer by 1.31-fold each. 7

Example 2 (A) One hundred and thirty-six (136) par-ts (2.57 moles) of acrylonitrile, 12 parts (0.14 mole) of vinyl acetate, 12 parts (0.10 mole) of 2-methyl-5-vinyipyridine, 4.02 parts (0.11 mole) of hydrogen chloride, and 980 parts of deionized Water are charged into a roundbottomed flask. The apparatus is assembled as in Example 1. The catalyst, 0.169 part (0.00159 mole) of sodium chlorate and 1.299 parts (0.0103 mole) of sodium sulfite, is dissolved in 150 cc. of water into a dropping funnel. Polymerization is conducted as in Example 1. The pH of the efiluent mother liquor is 2.2. In this example, the mole' ratio of sodium chlorate to monomer is 0.000566, while the mole ratio of sodium sulfite to monomer is 0.00367. Conversion of monomer to polymer is 7 55 percent of theory. The polymer has an average molecular Weight of 64,000.

(B) The above example is repeated, except that 1.33 parts (0.0125 mole) of sodium chlorate and 3.15 parts (0.0250 mole) of sodium sulfite are used. In this case,

parts (0.15 mole) of hydrogen chloride, and 980 parts of deionized Water are charged into a round-bottomed flask. The apparatus is assembled as in Example 1. The catalyst, 0.375 part (0.00352 mole) of sodium chlorate and 2.66

a parts (0.0211 mole) of sodium sulfite, is dissolved in the mole ratio of sodium chlorate to monomer is 0.00445, 150 cc. of Water into a dropping funnel. Polymerization while the mole ratio of sodium suliite to monomer is is conducted as in Example 1. The pH of the efiluent 0.00890. Conversion of monomer to polymer is 68 permother liquor is 2.0. In this example, the mole ratio of cent of theory. The polymer has an average molecular sodium chlorate to monomer is 0.00124, while the mole weight of 63,000. I ratio of sodium sulfite to monomer is 0.00746. Conver- A comparison of the and Portions of this Sion of monomer to polymer is 40 percent of theory. The example Shows that the Conversion of monomer to polymer has an average molecular weight of 88,000. P y Increase/d, and the avenge h f Welght (B) The above example is repeated, except that 1.875 maintained substantially constant, despite the increase 111 parts (0.0176 mole) of sodium chlorate and 6.65 parts the tta1 Catalyst used, y increasing the mole 0 0f 15 (0.0528 mole) of sodium sulfite are used. In this case, sod1um Chlorate t0 mohomfif y 73349151 along with a the mole ratio of sodium chlorate to monomer is 0.00623, simultaneous 2.43-fold increase of the m le ratio 0f while the mole ratio of sodium sultite to monomer is sod1um Sulfite h- 0.0187. Conversion of monomer to polymer is 72 percent If the mole ratio of sodium chlorate and sodium sulfite f h h polymer h an average molecular might to monomer are each increased by the same percent, the f 39 0 average molecular weight decreases as expected. A comparison f h (A) and 3 portions f this ample shows that the conversion of monomer to polymer Example 3 1 is increased, and the average molecutar weight is main- 101116 fOhOWlhg tests 144 P911715 moles) of tained substantially constant, despite the increase in total acrylonitrile, 8 parts (0.093 mole) of vinyl acet 8 catalyst used, by increasing the mole ratio of sodium Parts H1016) Y Y PY Part5 chlorate to monomer by 5 02-fold along with a simultane- H1016) of hydrogen Qhlorlda, and 930 Parts Of ous 2.51-fold increase of the mole ratio of sodium sulfite Ionized Water m6 Chargfid Into a found-bottomed flaskto monomer. If the mole ratio of sodium chlorate and pp assembled 1h Example Catalyst sodium white to monomer are each increased by the 15 dlswhfed m 150 of Water Into a pp funnelsame percent, the average molecular weight decreases as Polymerization is conducted as in Example 1. The pH expectay of the efiluent mother liquor is 2.4. Exmnple 5 A comparison of the (A-3) (13-2), and (C3) portions of this exampie shows that the conversion of 3 lfi j g fem; 3 3 4 parts monomer to polymer is increased and the average molecm0 i 01 Parts J e) y ular weight is maintained substantially constant by in- Wine, 3 Parts (3-070 1036) 0f Y P3 creasing the mole ratio of sodium siilfite to monomer Parts of hydl'ogi'ih \fhlorldfi, and 139 P along with a r o tio t ly re t ir re i th l of deionized Water are charged into a round-bottomed ratio of sodium chlorate to monomer. flask. The apparatus is assembled as in Example 1. The

Examination of tests (AL-5), (Bl5), (11-4), and 40 catalyst, 0.665 part (0.00624 mole) of sodium chlorate Parts Moles Mole ratio to Monomer n-Fold increase Con er- Tests above sample sion M.W.

l in each instance Percent (D14) shows that if the sodium chlorate to monomer and 3.93 parts (0.0312 mole) of sodium sulfite, i disand sodium sulfite to monomer ratios are varied in the solved in cc. of water into a dropping funnel. Polysame proportion, the molecular weight is inversely propormerization is conducted as in Example 1. The pH of tional to the amount of catalyst used. As the amount of catalyst used increases, the molecular weight of the resultant polymer becomes less dependent upon the amount of catalyst used. At high catalyst'quantity, the molecular weight is a function of the molar ratio of sodium chlorate to sodium sulfite and not a function of total catalyst.

Example 4 (A) One hundred and thirty-six (136 parts) (2.57 moles) of acrylonitrile, 13.5 parts (0.157 mole) of methyl the effluent mother liquor is 1.9. In this example, the mole ratio of sodium chlorate to monomer is 0.00216, While the mole ratio of sodium sulfite to monomer is 0.0108. Conversion of monomer to polymer is 64 percent of theory. The polymer has an average molecular weight of 53,000. V

(B) The above example is repeated, except that 1.28 parts (0.0120 mole) of sodium chlorate and605 parts (0.0480 mole) of sodium sulfite are used. in this case, the mole ratio of sodium chlorate to monomer is 0.00416,

acrylate, 10.5 parts (0.10 mole) of 2-vinylpy1idine, 5.47 7 while the mole ratio of sodium sulfite to monomer is 3,0 9 0.0166. Conversion of monomer to polymer is 72 percent of theory. The polymer has an average molecular weight of 53,000.

A comparison of the (A) and (B) portions of this example shows that the conversion of monomer to polymer is increased, and the average molecular weight is maintained substantially constant, despite the increase in total catalyst used, by increasing the mole ratio of sodium chlorate to monomer by 1.92-fold along with a simultaneous 1.53-ro1d increase of the mole ratio of sodium sulfite to monomer. If the mole ratio of sodium chlorate and sodium sulfite to monomer are each increased by the same percent, the average molecular Weight decreases as expected.

Example 6 (A) One hundred and sixty (160) parts (3.02 moles) of acrylonitrile, 1.2 parts (0.033 mole) of hydrogen chloride, and 1439 parts of deionized water are charged into a round-bottomed flask. The apparatus is assembled as in Example 1. The catalyst, 0.426 part (0.00400 mole) of sodium chlorate and 5.04 parts (0.0400 mole) of sodium sulfite, is dissolved in 150 cc. of Water into a dropping funnel. Polymerization is conducted as in Example l. The pH of the efiluent mother liquor is 2.9. In this example, the mole ratio of sodium chlorate to monomer is 0.00132, while the mole ratio of sodium sulfite to monomer is 0.0132. Conversion of monomer to polymer is 70 percent of theory. The polymer has an average molecular weight of 81,000.

(B) The above example is repeated, except that 1.02 parts (0.0096 mole) of sodium chlorate and 6.05 parts (0.0480 mole) of sodium sulfite are used. In this case, the mole ratio of sodium chlorate to monomer is 0.00318, while the mole ratio of sodium sulfite to monomer is 0059. Conversion of monomer to polymer is 84 percent of theory. The polymer has an average molecular weight of 79,000.

A comparison of the (A) and (B) portions of this example shows that the conversion of monomer to polymer is increased and the average molecular weight i maintained substantially constant, despite the increase in total catalyst used, by increasing the mole ratio of sodium chlorate to monomer by 2.41-fold along with a simultaneous 1.20-fold increase of the mole ratio of sodium sulfits to monomer. If the mole ratio of sodium chlorate and sodium sulfite to monomer are each increased by the same percent, the average molecular weight decreases as expected.

Example 7 (A) A water-jacketed reactor having a volume of 6.4 liters is supplied with a propeller-type stirrer, driven by a motor rotating at approximately 900 r.p.m. The reactor is equipped with a delivery-feed system; and, at its top, with an overflow tube. Polymer is collected by continuous filtration of the slurry overflow.

Six thousand four hundred (6,400) grams of water slurry containing polymer prepared in a previous similar reaction (seed polymer) is charged to the reactor, adjusted to a pH of about 2 with nitric acid, and its temperature is brought to 45 C. A stream of monomers introduced to the reactor through one of three delivery tubes. A second stream consists of an aqueous delivery tubes. A second stream consists of an aqueous solution of weighed amounts of sodium chlorate and sodium sullite. The third stream consists of an aqueous solution of nitric acid of known concentration.

Polymer produced during the first four hours of reaction is discarded. Under the conditions of reaction, it has been found that more than 92 percent of the seed polymer has been purged and that a steady state or equilibrium is set up before any polymer product is collected.

has?

The temperature of the reaction is maintained at 45 C. Monomer concentration and residence time are controlled by the feed rates at 28 percent monomer concentration and 1.5 hour residence time in the reactor. The pH is maintained at 2.0.

The composition of the feeds is as follows:

Feed IMonomers (85.9% acrylonitrile, 7.5% vinyl acetate, and 6.6% 2-vinyl pyridine) Feed II-Catalyst (51.7 grams of NaClO and 245.0

grams of Na SO in solution in 16 liters of water) Feed Ill-Acid (640 grams of HNO in solution in 16 liters of water) Monomers (feed I) are fed at 1410 cc./hr., 1155 grams/hr. Catalyst (feed II) is fed at 1430 cc./hr. Therefore, the rate of NaClO /hr. is 4.62 grams/hr. and the rate of Na SO /hr. is 21.9 grams/hr. Acid (feed III) is fed at 1430 cc./hr. At equilibrium, the conversion of monomer to polymer is 50 percent, The polymer has an average molecular Weight of 91,000.

(E) The above example is repeated in every detail, except that the catalyst (feed II) contains 116.2 grams of NaClO and 412.0 grams of Na SO in 16 liters of water. Since all feed rates are the same, the rate of NaClO /hr. is 10.4 grams/hr., and the rate of Na SO /hr. is 36.8 grams/hr. At equilibrium, the conversion of monomer to olymer is 67 percent. The polymer has an average molecular weight of 93,000.

A comparison of the (A) and (B) portions of this example shows that the conversion of monomer to polymer is increased and the average molecular weight is maintained substantially constant, desipte the increase in total catalyst used, by increasing the mole ratio of sodium chlorate to monomer by 2.25-fold along with a simultaneous 1.68-fold increase of the mole ratio of sodium sulfite to monomer. If the mole ratio of sodium chlorate and sodium sulfite to monomer are each increased by the same percent, the average molecular weight decreases as expected.

Example 8 (A) The procedure of Example 7 is followed, except for feed composition.

Feed IMonomers acrylonitrile, 5.0% vinyl acetate, 5.0% 2-methyl-5-vinyl pyridine) Feed IICatalyst (51.7 grams of NaClO and 183.5

grams of Na SO in 16 liters of water) Feed III--Acid (299 grams of HNO in solution in 16 liters of water) The rate of NaClO /hr. is 4.62 grams/hr. The rate of Na SO /h-r. is 16.4 grams/hr. The pH is maintained at 3.3. At equilibrium, the conversion of monomer to polymer is 78 percent of theory. The polymer has an average molecular weight of 71,000.

(B) The above example is repeated in every detail, except that the catalyst (feed II) contains 116.2 grams of NaClO and 275.0 grams of Na SO in 16 liters of water. Since all feed rates are the same, the rate of NaClO /hr. is 10.4 grams/hr., and the rate of Na SO /hr. is 24.6 grams/hr. At equilibrium, the conversion of monomer to polymer is 86 percent of theory. The polymer has an average molecular weight of 71,000.

A comparison of the (A) and (B) portions of this example shows that the conversion of monomer to polymer is increased and the average molecular weight is maintained substantially constant, despite the increase in total catalyst used, by increasing the mole ratio of sodium chlorate to monomer by 2.25-fold along with a simultaneous -fold increase of the mole ratio of sodium sulfite to monomer. If the mole ratio of sodium chlorate and sodium sulfite to monomer are each increased by the same percent, the average molecular Weight decreased as expected.

Example 9 (A) The procedure of Example 6 is followed, except for feed composition.

Feed IMonomers (85.0% acrylonitrile, 8.3% vinyl acetate, and 6.7% 4-vinyl-pyridine) Feed II-Catalyst (38.8 grams of NaClO and 183.5

grams of Na SO in solution in 16 liters of water) Feed IlI--Acid (512 grams of HNO in solution in 16 liters of water) The rate of NaClO /hr. is 3.47 grams/hr. The rate of Na sO /hr. is 16.4 grams/hr. The pH is maintained at 3.2. At equilibrium, the conversion of monomer to polymer is 42 percent of theory. The polymer has an average molecular weight of 72,000.

(B) The above example is repeated in every detail, except that the catalyst (feed II) contains 64.6 grams of NaClO and 229.5 grams of Na SO in liters of water. Since all feed rates are the same, the rate of NaClO /hr. is 5.77 grams/hr., and the rate of Na SO /hr. is 20.5 grams/ hr. At equilibrium, the conversion of monomer to polymer is 71 percent of theory. The polymer has an average molecular Weight of 72,000.

A comparison of the (A) and (B) portions of this example shows that the conversion of monomer to polymer is increased and the average molecular weight is maintained substantially constant, despite the increase in the total catalyst used, by increasing the mole ratio of sodium chlorate to monomer by 1.67-fold along with a simultaneous 1.25-fold increase of the mole ratio of sodium sulfite to monomer. If the mole ratio of sodium chlorate and sodium sulfite to monomer are each increased by the same percent, the average molecular weight decreases as expected.

This application is a continuation of our copending application Serial No. 711,117, filed January 27, 1958, and allowed March 13, 1961.

We claim:

1. The method which comprises preparing a reaction mass comprising a polymerizable material in an aqueous medium having a pH not higher than about 4.0 and having a content of said polymerizable material not greater than 50%, said polymeriz-able material being selected from the group consisting of (1) acrylonitrile and (2) mixtures containing more than 50% by weight of acrylonitrile, the balance being at least one other ditferent compound which is copolymerizable wit-h acrylonitrile and which contains a CH =C grouping; introducing into said reaction mass a redox-catalyst system comprising chlorate ions and sulfite ions, the amount of the chlorate ions being within the range of from about 0.1% to about 3% and that of the sulfite ions within the range of from about 0.1% to about 9%, said percentages being by weight of the said polymerizable material; polymerizing the reaction mass containing the said redox-catalyst system and polymerizable material; and, at any norm of chlorate ions and of sulfite ions within the aforementioned ranges of percentage proportions of said ions to said polymerizable material and while keeping the said reaction mass at a substantially constant temperature and at a substantially constant pH not higher than about 410, increasing the conversion of the said polymerizable material to polymer of substantially uniform average molecular weight by increasing above said norm the ratio of molar equivalents of sulfite ions to said polymerizable material together with an increase in the ratio of molar equivalents of chlorate ions to said polymerizable material that is greater than the increase above said norm in the ratio of molar equivalents of sulfite ions to said polymerizable material, the amounts of the chlorate and sulfite ions after said increases remaining, however, within the aforesaid ranges of from about 0.1% to about 3% of chlorate ions and about 0.1% to about 9% of sulfite ions based on the weight ofvsaid polymerizable material.

2. A method as in claim 1 wherein the amount of 12 the chlorate ions is within the range of from about 0.1% to about 2% and that of the sulfite ions within the range of from about 0.1% to about 6%, the said percentages being based on the weight of polymerizable material defined in claim 1.

3. The method which comprises preparing a reaction mass comprising a monomeric polymerizable material in an aqueous medium having a pH of from about 2.0 to about 3.6 and having a content of said polymerizablc material not greater than 50%, said monomeric material being selected from the group consisting of (1) acrylonitrile and (2) mixtures containing more than 50% by weight of acrylonitrile, the balance being at least one other different compound which is copolymerizable with acrylonitrile and which contains a CH =C grouping; introducing into said reaction mass a redox-catalyst system comprising chlorate ions and sulfite ions, the amount of the chlorate ions being within the range of from about 0.1% to about 2% and that of the sulfite ions within the range of from about 0.1% to about 6%, said percentages being by Weight of the said monomeric polymerizable material; polymerizing the reaction mass containing the said redox-catalyst system and monomeric polymerizable material; and, at any norm of chlorate ions and of sulfite ions within the aforementioned ranges of percentage proportions of said ions to said monomeric material and while keeping the said reaction mass at a substantially constant temperature and at a substantially constant pH between about 2.0 and about 3.6, increasing the conversion of the said polymerizable material to polymer of substantially uniform average molecular weight by increasing above said norm the ratio of molar equivalents of sulfite ions to said polymerizable material together with an increase in the ratio of molar equivalents of chlorate ions to said polymerizable material that is greater than the increase above said norm in the ratio of molar equivalents of sulfite ions to said polymerizable material, the amounts of the chlorate and sulfite ions after said increases remaining, however, Within the aforesaid ranges of from about 0.1% to about 2% of chlorate ions and about 0.1% to about 6% of sulfite ions based on the weight of said polymerizable material.

4. A method as in claim 3 wherein the chlorate and sulfite ions are derived from sodium chlorate and sodium sulfite, respectively.

5. A method as in claim 3 wherein the polymerizable material comprises at least 70% by weight of acrylonitrile.

6. The method which comprises preparing a reaction mass comprising monomeric material in an aqueous medium having a pH of from about 2.0 to about 3.6 and having a content of said material not greater than 50%, said monomeric material comprising at least by Weight of acrylonitrile, from 2 to 15% by weight of vinyl acetate, and from 2 to 15% by weight of a vinylpyridine; introducing into said reaction mass a redox-catalyst system comprising chlorate ions and sulfite ions derived from sodium chlorate and sodium sulfite, respectively, the amount of the chlorate ions being within the range of from about 0.1% to about 2% and that of the sulfite ions within the range of from about 0.1% to about 6%, said percentages being by weight of the said monomeric material; polymerizing the reaction mass containing the said redox-catalyst system and monomeric material; and, at any norm of chlorate ions and of sulfite ions within the aforementioned ranges of percentage proportions of said ions to said monomeric material and while keeping the said reaction mass at a substantially constant temperature and at a substantially constant pH between about 2.0 and about 3.6, increasing the conversion of the said monomeric material to polymer of substantially uniform average molecular weight by increasing above said norm the ratio of molar equivalents of sulfite ions to said monomeric material together with an increase in a. LA.

the ratio of molar equivalents of chlorate ions to said monomeric material that is greater than the increase above said norm in the ratio of molar equivalents of sulfite ions to said monomeric material, the amounts of the chlorate and sulfite ions after said increases remaining, however, within the aforesaid ranges of from about 0.1% to about 2% of chlorate ions and about 0.1% to about 6% of sulfite ions based on the weight of said monomeric material.

7. The method which comprises polymerizing, in an aqueous medium having a pH not higher than about 4.0 and using a redox-catalyst system comprising chlorate ions and sulfite ions, a polymerizable material selected from the group consisting of (1) acrylonitrile and (2) mixtures containing more than 50% by weight of acrylonitrile, the balance being at least one other different compound which is copolymerizable with acrylonitrile and which contains a CH =C grouping, the content of said polymerizable material in the aqueous medium being not greater than 50% and the amount of the aforesaid chlorate ions being within the range of from about 0.1% to about 3% and that of the aforesaid sulfite ions within the range of from about 0.1% to about 9%, said percentages being by Weight of the said polymerizable material; and, at any norm of chlorate ions and of sulfite ions within the aforementioned ranges of percentage proportions of said ions to said polymerizable material and while keeping the reaction mass at a substantially constant temperature and at a substantially constant pH not higher than about 4.0, increasing the conversion of the said polymerizable material to polymer of substantially uniform average molecular weight by increasing above said norm the ratio of molar equivalents of sulfite ions to said polymerizable material together with an increase in the ratio of molar equivalents of chlorate ions to said polymerizable material that is greater than the increase above said norm in the ratio of molar equivalents of sulfite ions to said polymerizable material, the amounts of the chlorate and sulfite ions after said increases remaining, however, within the aforesaid ranges of from about 0.1% to about 3% of chlorate ions and about 0.1% to about 9% of sulfite ions based on the weight of said polymerizable material.

References Cited in the file of this patent UNITED STATES PATENTS 2,628,223 Richards Feb. 10, 1953 2,673,192 Hill Mar. 23, 1954 2,751,374 Cresswell June 19, 1956 2,769,793 Ham Nov. 6, 1956 2,777,832 Mallison Jan. 15, 1957 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,028 372 April 3, 1962 Witold R. Kocay et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column l line 24 strike out "organizable"; column 2 line 2 after "grouping" insert a comma; column 4, line 33, for "the", first occurrence, read their column 9, line 65, strike out "tubes. A second stream consists of an aqueous delivery"; column 10, line 33, for "desipte" read despite line 74, for "decreased" read decreases column 11, line 18, before "liters" insert l6 Signed and sealed this 17th day of July 1962o (SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents 

1. THE METHOD WHICH COMPRISES PREPARING A REACTION MASS COMPRISING A POLYMERIZABLE MATERIAL IN AN AQUEOUS MEDIUM HAVING A PH NOT HIGHER THAN ABOUT 4.0 AND HAVING A CONTENT OF SAID POLYMERIZABLE MATERIAL NOT GREATER THAN 50%, SAID POLYMERIZABLE MATERIAL BEING SELECTED FROM THE GROUP CONSISTING OF (1) ACRYLONTRILE (2) MIXTURES CONTAINING MORE THAN 50% BY WEIGHT OF ACRYLONITRILE, THE BALANCE BEING AT LEAST ONE OTHER DIFFERENT COMPOUND WHICH IS COPOLYMERIZABLE WITH ACRYLONTRILE AND WHICH CONTAINS A CH2=C> GROUPING; INTRODUCING INTO SAID REACTION MASS A REDOX-CATALYST SYSTEM COMPRISING CHLORATE IONS AND SULFITE IONS THE AMOUNT OF THE CHLORATE IONS BEING WITHIN THE RANGE OF FROM ABOUT 0.1% TO ABOUT 3% AND THAT OF THE SULFITE IONS WITHIN THE RANGE OF FROM ABOUT 0.1% TO ABOUT 9%, SAID PERCENTAGES BEING BY WEIGHT OF THE SAID POLYMERIZABLE MATERIAL; POLYMERIZING THE REACTION MASS CONTAINING THE SAID REDOX-CATALYST SYSTEM AND POLYMERIZABLE MATERIAL; AND AT ANY NORM OF CHLORATE IONS AND OF SULFITE IONS WITHIN THE AFOREMENTIONED RANGES OF PERCENTAGE PROPORTIONS OF SAID IONS TO SAID POLYMERIZABLE MATERIAL AND WHILE KEEPING THE SAID REACTION MASS AT A SUBSTANTIALLY CONSTANT TEMPERATURE AND AT A SUBSTANTIALLY CONSTANT PH NOT HIGHER THAN ABOUT 4.0, INCREASING THE CONVERSION OF THE SAID POLYMERIZABLE MATERIAL TO POLYMER OF SUBSTANTIALLY UNIFORM AVERAGE MOLECULAR WEIGHT BY INCREASING ABOVE SAID NORM THE RATIO OF MOLAR EQUIVALENTS OF SULFITE IONS TO SAID POLYMERIZABLE MATERIAL TOGETHER WITH AN INCREASE IN THE RATIO OF MOLAR EQUIVALENTS OF CHLORATE IONS TO SAID POLYMERIZABLE MATERIAL THAT IS GREATER THAN THE INCREASE ABOVE SAID NORM IN THE RATIO OF MOLAR EQUIVALENTS OF SULFITE IONS TO SAID POLYMERIZABLE MATERIAL, THE AMOUNTS OF THE CHLORATE AND SULFITE IONS AFTER SAID INCREASE REMAINING HOWEVER, WITHIN THE AFORESAID RANGES OF FROM ABOUT 0.1% TO ABOTU 3% OF CHLORATE IONS AND ABOUT 0.1% TO ABOUT 9% OF SULFITE IONS BASED ON THE WEIGHT OF SAID POLYMERIZABLE MATERIAL. 